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In this study, experimental tests to assess rolling contact fatigue in uncoated and coated steel substrates with TiN and CrN coatings are presented. A thrust bearing tester was used. The tests were carried out in lubricated conditions at 1560 r/min, using a contact pressure of 2.09 GPa. The surface damage was analyzed by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. The substrates coated with CrN showed a fatigue life above 100 million cycles. On the other hand, with TiN, the time for crack nucleation was much shorter, approximately 60 × 104 cycles.

There are a number of different mechanisms by which tooth wear occurs, including tooth-tooth contact, temperature changes and the chemical environment inside the mouth; these different mechanisms can occur simultaneously. 'Attrition', 'abrasion', 'abfraction' and 'erosion' are the main terms used to describe tooth wear. Abrasion occurs in the presence of abrasive particles from various sources. Damage by abrasion occurs on enamel or dental porcelain surfaces when particles become trapped in the occlusal zone, a mechanism called three-body wear abrasion. In the current study, three commercial dental powder-liquid porcelains (used as restoratives in posterior teeth) and one amalgam restorative were tested using an in vitro method with a Plint TE66 microwear tester. Wear conditions were 0?25 N of load applied, 0?1 m s 21 of ball speed and 7?98 m of sliding distance at room temperature. Mixtures of distilled water and artificial saliva were used as liquid suspension, each containing 22 vol.-% silicon carbide (SiC F1200), with an average size of 4 mm. Lost volume and wear coefficient of the restoratives were determined. Scanning electron microscopy images were obtained, the wear patterns (scars) on the specimens were analysed and the wear mechanisms (including brittle fractures for the porcelains, and ploughing, cutting and plastic deformation for the amalgam) were identified and discussed. Wear topography was obtained from atomic force microscopy images.

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